1. Field of the Invention
The present invention relates to an organic electroluminescent device, particularly to an organic electroluminescent device having the structure capable of dispensing a sealant uniformly on the entire cap-bonding area of a substrate.
2. Description of the Related Art
Organic electroluminescence is the phenomenon that excitons are formed in an (low molecular or high molecular) organic material thin film by re-combining holes injected through an anode with electrons injected through a cathode, and a light of specific wavelength is generated by energy from the formed excitons.
Organic electroluminescent device using the above phenomenon has the basic structure as shown in FIG. 1. The basic structure of organic electroluminescent device includes a glass substrate 1, indium-tin-oxide layers 2 (hereinafter, referred as “anode electrodes”) formed on the glass substrate 1 and acting as anode electrode, an insulating layer, an organic electroluminescence layer 3 formed with organic material, and metal layers 4 (hereinafter, referred as “cathode electrodes”) acting as cathode electrode. Walls W are formed to deposit the cathode electrodes 4 into a number of sections on the anode electrodes 2.
The structural elements constituting the organic electroluminescent device are well known in the field. Therefore, a detailed description thereon is omitted.
After the active area consisted of the structural elements 2, 3, 4 and W shown in FIG. 1 is formed, a cap 6 is bonded to a periphery of the substrate 1 by using a sealant 5. The area onto which the cap is bonded is an outer portion of the substrate 1, that is, an outer area of the active area. The active area is completely separated from the exterior by the cap 6, and only end portions of the anode electrodes 2 and the cathode electrodes 4 are exposed to the exterior.
As shown in FIG. 1, a sealed space is formed between the cap 6 and the substrate 1, and the structural elements 2, 3, 4 and W placed in this space are not influenced by the exterior environment such as moisture and the like. On the other hand, the cap 6 is made of glass or metal, and an ultraviolet rays-cured adhesive is used as the sealant 5. Also, a getter 8 of moisture absorbent is attached to the lower surface of the cap 6 by a tape 7 (made of organic material)
FIG. 2 is a plane view of the organic electroluminescent device. For convenience's sake, FIG. 2 shows a state that the cap 6 is removed from the organic electroluminescent device shown in FIG. 1. Also, in FIG. 2, the active area A consisted of the structural elements 2, 3, 4 and W shown in FIG. 1 is illustrated in the form of box.
As shown in FIG. 2, a plurality of anode electrodes 2 and a plurality of cathode electrodes 4 formed in the active area A are extended to an outer portion of the active area A, and the end portions of the extended anode electrodes 2 and cathode electrodes 4 (that is, data lines and scan lines) are concentrated at one region of the substrate 1 to form a pad section P.
Hereinafter, on the other hand, a plurality of data lines 2 and a plurality of scan lines 4 extended to an outer portion of the active area A are referred to as “the data line group 2A” and “the scan line group 4A,” respectively.
The process for bonding the cap 6 to the substrate 1 as described above is briefly described with reference to FIG. 1 and FIG. 2 below.
After the getter 8 is attached to the cap 6 loaded on a cap tray (not shown), the sealant 5 is dispensed on the substrate-bonding area of the cap 6 (corresponding part to the cap-bonding areas S1 and S2 of an outer portion of the substrate 1) or the cap-bonding areas S1 and S2 of the substrate 1. After the substrate 1 and the cap 6 are aligned, the cap 6 is bonded to an outer portion S1 and S2 of the active area A formed on the substrate 1. And, in order to secure the bonding state of the cap 6, ultraviolet rays are radiated selectively onto the cap-bonding areas S1 and S2 of the substrate 1 to cure the sealant 5.
As shown in FIG. 2, the end portions of the scan line group 4A and the data line groups 2A are concentrated and arranged on the pad section P of the substrate 1, and certain space S is formed between the scan line group 4A and the data line group 2A at the cap-bonding area S1 of the substrate 1 adjacent to the pad section P as indicated by “K.” However, this space S prevents the sealant from being uniformly dispensed.
FIG. 3 is a bottom view of the cap, and shows a state the sealant is dispensed on the lower surface of a periphery of the cap 6. In FIG. 3, the peripheries C1 and C2 on which the sealant 5 is dispensed correspond to the cap-bonding areas S1 and S2 of the substrate in FIG. 2.
In the process of dispensing the sealant 6 onto the cap 5 through a dispenser (not shown), the sealant 5 is not dispensed on each corner of the cap 6 due to the operational characteristic of the dispenser. In this state, when the cap 6 is pressurized to the substrate 1, the sealant 5 dispensed on the peripheries C1 and C2 is flowed toward each corner section. Accordingly, the sealant 5 is dispensed onto all peripheries of the cap 6 corresponding to the cap-bonding areas S1 and S2 of an outer portion of the active area A of the substrate 1 to bond the cap 6 and the substrate 1.
FIG. 4 is a partial sectional view of “K” section in FIG. 2, assuming that the sealant 5 is dispensed on the cap-bonding area S1 of the substrate 1. As illustrated there, the sealants dispensed by the dispenser is not dispensed on each corner section of the substrate 1, and the amount of sealant dispensed on the end portions of the cap-bonding area S1 is much less than other portion of the cap-bonding area.
In this state, when the cap 6 is pressurized to the substrate 1, the sealant 5 is flowed toward the end portion of the cap-bonding area S1 (the arrow direction in FIG. 5). In the course that the sealant 5 moves toward the end portion of the cap-bonding area S1 by pressure from the cap 6, the sealant 5 is flowed into the space S formed between the scan line group 4A and the data line group 2A, to fill the whole space S.
By filling the space S, the amount of the sealant 5 flowed toward the scan line group 4A is decreased, and the scan lines 4 act as an obstacle preventing flow of the sealant. Accordingly, the sealant cannot be dispensed uniformly onto both end portions of the cap-bonding area S1 of the substrate 1 (that is, the scan line groups 4A).
Although the cap 6 can be bonded to the substrate 1 under this condition, the space between the cap 6 and the substrate 1 is not completely sealed due to the area on which the sealant 5 is not dispensed, resulting in exposing the structural elements of the device to the exterior environment.